System and method for transmitting data from a server application to more than one client node

ABSTRACT

A system and method for transmitting the same data to more than one client node or from an application to at least two client nodes. The method includes connecting a first client node and a first client protocol stack and connecting the application and the first client protocol stack; associating a first minimal communications protocol stack with the first client protocol stack; providing a connection between the application and the first minimal communications protocol stack and between a second client node and a second client protocol stack; associating a second minimal communications protocol stack with the second client protocol stack; providing a connection between the first minimal protocol stack and the second minimal protocol stack; and between the second minimal protocol stack and said the client protocol stack. Data is then transmitted from the application program to the first client protocol stack and the first minimal protocol stack substantially simultaneously.

FIELD OF THE INVENTION

The present invention relates generally to a system and method forcommunicating between a server application and multiple client nodes andmore specifically to a system and method for transmitting the same datato more than one client node substantially simultaneously.

BACKGROUND OF THE INVENTION

Shadowing (transmitting data destined for one client node substantiallysimultaneously to a second client node) and broadcasting (transmittingthe same data substantially simultaneously to more than one client node)typically has been performed using a specialized transmittingapplication on a server node and specialized receiver applications oneach of the client nodes. Shadowing is useful in monitoring data trafficand for creating a redundant copy of information being transmitted fordata integrity and system security purposes. Broadcasting is useful inproviding the same information to many users, when such information is“real-time” or when the information does not have a per se beginning orending. For example, a stock price quotation program simply transmitsthe current prices of various stocks on a given exchange and the listrepeats with the latest prices once the list of stocks is exhausted.Thus it is irrelevant to a user that he or she does not specify to thequotation program where to begin the list.

Such programs typically are written with a broadcast program in mind andrequire specialized receiver programs to receive the data transmitted.If an application has not been written as a broadcast program, the datatransmitted by such an application can not typically be broadcast tomultiple client nodes.

The present invention attempts to overcome this problem by permittingprograms not written for broadcast functionality to be used to broadcastdata over a network.

SUMMARY OF THE INVENTION

The invention relates to a system and method for transmitting the samedata to more than one client node substantially simultaneously. In oneembodiment the invention relates to a method for transmitting the samedata substantially simultaneously from an application executing on aserver node to at least two client nodes executing a generalizedreceiver program. The method includes the steps of establishing aconnection between a first client node and a first client protocol stackon the server node; establishing a connection between the applicationexecuting on the server node and the first client protocol stack;associating a first minimal communications protocol stack with the firstclient protocol stack; establishing a connection between the applicationexecuting on the server node and the first minimal communicationsprotocol stack; establishing a connection between a second client nodeand a second client protocol stack on the server node; associating asecond minimal communications protocol stack with the second clientprotocol stack; providing a connection between the first minimalprotocol stack and the second minimal protocol stack; providing aconnection between the second minimal protocol stack and said the secondclient protocol stack; and transmitting data from the applicationprogram to the first client protocol stack and the first minimalprotocol stack, substantially simultaneously.

The invention also relates to a communication system including a serverand two or more client nodes. In one embodiment the server nodecomprises an application program; a first client protocol stack inelectrical communication with the application program; a first minimalprotocol stack in electrical communication with the application program;a second minimal protocol stack in electrical communication with thefirst minimal protocol stack; and a second client protocol stack inelectrical communication with the second minimal protocol stack. Inaddition the system includes a first client node in electricalcommunication with the first client protocol stack and a second clientnode in electrical communication with the second client protocol stack.Data from the application program is transmitted to the client protocolstack and the first minimal protocol stack substantially simultaneously.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures depict certain illustrative embodiments of theinvention in which like reference numerals refer to like elements. Thesedepicted embodiments are to be understood as illustrative of theinvention and not as limiting in any way.

FIG. 1 is a highly schematic diagram of an embodiment of a communicationsystem utilizing the invention;

FIG. 2 is a block diagram of an embodiment of the invention showing theconnections between various components of the server of FIG. 1 whichoccur during communication between the clients and server;

FIG. 3 is a block diagram of an embodiment of the invention thatmaintains and manages multiple client node connections;

FIG. 4 is a block diagram of an embodiment of the system for embeddingapplications in an HTML page;

FIG. 5 is a diagrammatic view of a client node;

FIG. 6 is a block diagram of an embodiment of the invention depictingthe use of a multiplexer to transmit the same data from an applicationto more than one client; and

FIG. 7 is a block diagram of the embodiment of the invention in whichthe broadcast capabilities are increased by fan out.

DETAILED DESCRIPTION

Referring now to FIG. 1, in brief overview, a typical network 20includes at least one client node 24, at least one server node 34, 34′,and a master network information node 40 connected together by acommunications link 44. The embodiment shown in FIG. 1 depicts thecommunications link 44 as a local area network ring or LAN ring, but anycommunication topology may be used. For the purpose of explanation theserver node 34 is assumed to have the application requested by theclient node 24. Also, for the purpose of explanation, the master networkinformation node 40 is assumed to be a distinct server node, but inactuality the master network information node 40 may be an applicationexecution server node 34. It should be noted that on a given LAN severalnodes may be capable of acting as a network information node, but at anyone time only one of such nodes is designated the master networkinformation node 40 for the system 20 and it is to this node that clientrequests for server information are directed.

The master network information node 40 maintains a table of addressesfor the application execution server nodes 34, 34′. In addition, themaster network information node 40 receives messages from eachapplication execution server node 34, 34′ indicating its level ofactivity. The level of activity of the application execution servernodes 34, 34′ is maintained in a table along with the address of each ofthe application execution server nodes 34 and is used by thecommunications system 44 for load leveling.

When the client 24 wishes to have an application executed on anapplication execution server node 34, the client node 24 sends a requestto the general communications port previously defined by thecommunications protocol or to the “well-known” communications port onthe master network information node 40. In one embodiment thecommunication takes place by way of a datagram service. The masternetwork information node 40 accesses the table of server addresses andreturns a message containing the address of the application executionserver or lo application server 34 which has the requested applicationand also which has the least load. Subsequent communications areautomatically addressed by the client also to a “well-known” orpredefined general communications port on the server node 34. In oneembodiment, the type of protocol with which the initial query was madeto the master network information node 40 determines the protocol of theinformation returned by the master network information node 40 to theclient node 24. Thus if the request were made using a TCP/IP datagram,the master network information node 40 would return the TCP/IP addressof the server 34 to the client node 24 and the client node 24 wouldsubsequently establish contact with the server node 34 using thatprotocol. In another embodiment, the datagram requesting an applicationaddress by a client 24 includes a request for a different type ofprotocol than the one used to send the request to the master networkinformation node 40. For example, the client 24 may make a request tothe master network information node 40 using the IPX protocol andrequest the address of the application server as a TCP/IP protocoladdress.

When a client node 24 (actually a client process 56 on a client node 24)desires to communicate with an application on a server node 34, 34′ theclient node 24 begins by issuing a network request to determine thelocation of the server 34 having the desired application. This requestis received by the master network information node 40 (also referred toas a network browser 40) residing somewhere on the network. In this FIG.1, the network browser 40 is shown for simplicity as residing on adifferent server 40 from the server which has the application, but suchmay generally not be the case.

The master network information node 40 returns the network address ofthe server node 34 having the desired application to the client node 24.The client node 24 then uses the information received from the masternetwork information node 40 to request connection to the applicationexecuting on the specified server 34. As is described above, such aconnection is first established to a “well-known” communications portand is later transferred to a specific communications port under controlof a connection manager. The specific communications port is associatedwith the application executing on the server node 34 which thencommunicates with the client node 24 through the specific communicationsport.

In more detail, and referring to FIG. 2, the client process 56 on clientnode 24 makes a request 54 to the master network information node 40 toobtain the address of a server node 34 which includes the desiredapplication 62. The master network information node 40 returns to theclient node 24 a message 58 containing the address of the server node 34which includes the server application 62. In one embodiment, theprotocol used at this point of the connection is a datagram service.

The client node 24 uses the returned address to establish acommunication channel 68 with the server 34. The port number used by theclient 24 corresponds to the “well-known port” in the server 34 whichhas been defined by the network protocol as the port by which the server34 establishes communication connections with clients 24. The well-knownport 72 has a rudimentary protocol stack 76 which includes primarily anend point data structure 78.

The end point data structure 78 points to the communication protocolstack 76 and client connection thereby establishing a uniquerepresentation or “handle” for the client 24. The end point datastructure 78 permits the connection between the server 34 and the client24 to be moved at will between the connection manager 80 and the variousapplications 62 on the server 34. The end point data structure 78, inone embodiment, not only contains the handle to the client 24 but mayalso contain other information relating to the client connection. In theembodiment shown, the application server 34 monitors activity on aspecific communications system (e.g. LAN or WAN) and has initializedthis minimum protocol stack 76 with only the necessary protocol modulesneeded to support a “TTY” communication mode. The “TTY” communicationmode is a simple ASCII stream with no protocol assumptions above thetransport layer. That is, there are no protocol layers for compression,encryption, reliability, framing, or presentation of transmitted data.Thus a client node 24 seeking an application 62 running on the server 34establishes a connection to the well-known communications port 72 withthe minimum protocol set needed to support a TTY communication mode.

A connection manager 80 executing on the server node 34 is “listening”to the well-known communications port 72 for a connection request 68.When a connection request 68 is received from the client node 24, theconnection manager 80 is notified 84. The connection manager 80 knowswhich protocol is being used based on the notification 84.

With this information the connection manager 80 creates a new minimumprotocol communications stack 104, starts the execution environment 96and binds the new minimum protocol stack 104 to the executionenvironment 96. In one embodiment, the server 34 includes a number ofexecution environments 96 which have been previously been started, butwhich have not been associated with a communications port. In thisembodiment, the pre-connection starting of the execution environmentspermits a faster response time than if each execution environment 96 isstarted when the connection request is received from the client 24. Whenthe execution environment 96 is started, the server application 62requested by the client 24 is also started. In another embodiment, ifthe client 24 does not specify an application, either a defaultapplication is started or simply the execution environment 96 with noapplication is started.

The connection manager 80 then moves the client connection, includingthe unique client identifier or handle, from the well-known port 72 tothe new minimum protocol stack 104. The connection manager 80, using theminimum protocol stack sends a TTY data stream that indicates service isavailable. Thus, this method for detecting a client connection isindependent of the port to which the connection is first established. Ifthe client node 24 does not respond within a prescribed time period(e.g. 5 seconds) to the service available message, a resends of the“service available” message is performed by the server 34.

If the client 24 receives the message, the client 24 sends a TTY stringindicating that the “service available” message was detected. The client24 waits for the server 34 to respond and if the response is not withina prescribed time interval (e.g. 5 seconds) the client 24 resends themessage. The connection manager 80 then queries 90 the client 24 askingfor the client's default communication parameters. This query 90 takesthe form of a message which is passed back to the client 24 and whichindicates that the client 24 should respond with details regarding whatprotocols the client 24 would like to use in the connection.

In response, the client 24 sends a set of protocol packets 92; eachpacket of which is used to specify a required or optional protocolmodule that is being requested from the server 34. In one embodiment,the number of packets in the set is variable with one packet being sentfor each protocol requested. In another embodiment, the number ofpackets that is being sent is included in the header of the firstpacket. In a third embodiment, the remaining number of packets beingsent is included in the header of each packet and is decremented witheach succeeding packet sent. Thus, the client 24 may respond to thequery 90 by indicating that, for example, encryption and datacompression will be used. In such a case, two protocol packets will besent from the client 24 to the server 34 and, in one embodiment, theheader of the first packet will indicate the number of packets as two.

Once the responses to the query 90 have been received, the connectionmanager 80 builds a protocol stack using protocol drivers 120, 120′,120″ which correspond to the protocols requested by the client node 24.In one embodiment, the connection manager 80 places each of the requiredprotocol drivers 120, 120′, 120″, corresponding to the requested clientprotocols (e.g. an encryption driver if encryption is desired by theclient) into the protocol stack “container” 112 and links them together.This dynamic process allows a client node 24 to specify the contents ofa protocol stack dynamically without requiring that the server 34 have aprior protocol stack description for a particular client node 24. Usingthis method, multiple clients 24 may be served by a single server, evenif the separate clients 24 have vastly differing requirements for theassociated communications channel. In the embodiment shown, each client24, 24′, 24″ is associated with a respective communications protocolstack 104, 104′ and 104″. Such dynamically extensible protocol stacksare described in more detail below and in U.S. patent application Ser.No. 08/540,891, filed on Oct. 11, 1995 and incorporated herein byreference.

In the embodiment just discussed, the “container” 112 is a user level orkernel level device driver, such as an NT device driver. This containerdriver provides ancillary support for the inner protocol modules or“drivers” (generally 120) which correspond to the protocol requirementsof the client node 24. This ancillary support is in the form of helperroutines that, for example, aid one protocol driver to transfer data tothe next driver. Alternatively, in another embodiment each protocoldriver is a complete user-level or kernel-level driver in itself.

Referring now to the embodiment depicted in FIG. 3, the connectionmanager 80 includes two main software modules: ICASRV.EXE 90 andICAAPI.DLL 94. In the embodiment shown, ICASRV.EXE 90 is the server sideof a client/server interface. ICASRV.EXE 90 manages all communicationsstates and is, in one embodiment, implemented as a WINDOWS NT™ service.A second part of the connection manager 80 is ICAAPI.DLL 94. ICAAPI.DLL94 establishes the connection with the client, establishes the protocolsto be used and notifies ICASRV.EXE 90 of the completion of the protocolstack. In one embodiment, a third module CDMODEM.DLL 96 is linked toICAAPI.DLL 94′. CDMODEM.DLL 96 is a module which ICAAPI.DLL 94′ uses tocommunicate with modem devices.

The connection methodology described above can be used for a client 24running a Web browser program. For the purposes of this specification,the user running the Web browser program will be referred to as the“viewing user.” The terms “server” or “server node” will be used torefer to machines hosting HTML files or applications that may beexecuted. For example, a viewing user runs a Web browser on a clientnode and makes file requests via the HTTP protocol to servers. Theservers respond by transmitting file data to the client via the HTTPprotocol. The Web browser run on the client receives the transmitteddata and displays the data as an HTML page to the viewing user.

In brief overview and referring to FIG. 4, an HTML file 64 located on aserver 34′ and constructed in accordance with an embodiment of theinvention includes a generic embedded window tag 66. The genericembedded window tag 66 is any data construct which indicates to abrowser 60 displaying the HTML file 64 that a generic embedded window66′ should be displayed at a particular location in the HTML page 64′described by the HTML file 64. The generic embedded window tag 66 mayinclude additional information, such as height of the window, width ofthe window, border style of the window, background color or pattern inthe window, which applications may be displayed in the window, how oftenthe output display should be updated, or any other additionalinformation that is useful to enhance display of the application output.

Some examples of generic embedded window tags that can be embedded in anHTML file follow.

ActiveX tag <object classid=“clsid:238f6f83-b8b 4-1lcf-8771-00a024541cc3” data=“/ica/direct.ica”CODEBASE=“/cab/wfica.cab” width=436height=295> <param name=“Start” value=“Auto”> <param name=“Border”value=“On”></object> Netscape Plugin tag <embedsrc=“http://www.citrix.com/ica/direct.ica”pluginspage=“http://www.citrix.com/plugin.html” height=295 width=436Start=Auto Border=On><embed> JAVA tag <applet code=JICA.class width=436height=295> <param name=Address value=“128.4.1.64”> <paramname=InitialProgram value=Microsoft Word 7.0> <param name=Startvalue=Auto> <param name=Border value=On></applet>

In each case above, the tag indicates that a window having a height of295 pixels and a width of 436 pixels should be drawn to receiveapplication output. Each tag also specifies that the application shouldautomatically start execution and that the window in which theapplication output is displayed should be drawn with a border. TheActiveX and Netscape Plugin tags have the remote application parametersspecified in the file “direct.ica” located in the directory “/ica.” TheJAVA tag specifies the remote application parameters directly. In theexample above, the address of the server hosting the application isspecified as well as the name of the application to be executed.

The browser application 60 accesses the HTML file 64 by issuing arequest to a specific Uniform Resource Locator (URL) address. The server34′ hosting the HTML file 64 transmits the HTML file 64 data to thebrowser application 60, which displays text and translates any tags thatare included in the HTML file 64. The browser application 60 displaysthe HTML file 64 data as an HTML page 64′. If a generic embedded windowtag 66 is present in the HTML file 64, such as one of the tags describedabove, the browser 60 draws a blank window 66′ in the displayed HTMLpage 64′.

Execution of the desired application 62′ may commence immediately upondisplay of the HTML page 64′ or execution may await some signal, e.g. aspecified user input which indicates execution of the application 62′should begin. Once execution of the application 62′ is commenced, thebrowser application 60 instantiates a parameter handler 40 associatedwith the application window 66′. The parameter handler 40 instance maybe spawned as a child process of the browser application 60, as a peerprocess of the browser application 60, or as a Dynamically LinkedLibrary (“DLL”) associated with the browser application 60.

The browser application 60 passes any specific parameters associatedwith the application window 66′ that were provided by the genericembedded window 66 tag to the parameter handler 40 instance.Additionally, the browser application 60 may pass the handle for theapplication window 66′ to the parameter handler 40 instance or theparameter handler 40 instance may query the browser application 60 toretrieve the handle for the application window 66′. The parameterhandler 40 instance also spawns a network executive 50. The networkexecutive 50 may be spawned as a child process of the parameter handler40 instance or as a peer process of the parameter handler 40 instance.

The parameter handler 40 instance forwards any specified applicationwindow 66′ parameters to the network executive 50. Parameters which arenot specified by the parameter handler 40 instance or the embeddedgeneric window tag 66 may be set to default values. The networkexecutive 50 may have certain parameter defaults hard-coded, or thenetwork executive 50 may access a file which contains parameterdefaults.

The network executive 50 creates its own application output window 66″.The network executive 50 creates its application output window 66″ as achild of the displayed application window 66′ and displays itsapplication output window 66″ directly over the parent window 66′ drawnby the browser application 60. Since the application output window 66″drawn by the network executive 50 is a child of the application window66′ drawn by the browser application 60, the application output window66″ inherits various properties of its parent including positioninformation. Accordingly, the application output window 66″ will followthe application window 66′ as the viewing user scrolls the screen of thebrowser application 60 or performs other actions which vary the positionof the application window 66′.

The network executive 50 also establishes a communications channel withthe server 34 and invokes execution of the desired application 62′ bythe server 34″ using the connection methodology described above. Thenetwork executive 50, which acts as the client in the above description,passes any parameters it received from the parameter handler 40instantiation to the server, along with any necessary default values. Ifa parameter is not passed to the server, the server may request theparameter if it is a necessary parameter which has no default value,e.g. “user id,” or it may provide a default value for the parameter,e.g. execution priority. The server 34″ begins execution of the desiredapplication program 62′ and directs the output to the network executive50. The network executive 50 receives data from the application program62′ and displays the output data in its application output window 66″.Since the application output window 66″ is drawn on top of theapplication window 66′ drawn by the browser application 60, theapplication output data is displayed in the HTML page 64′. As notedabove, the application output window 66″ drawn by the network executive50 is a child of the application window 66′ drawn by the browserapplication 60. This allows the application output window 66″ to scrollas the HTML page 64′ is scrolled.

The application output window 66″ also receives input from the viewinguser. Raw input data, e.g. a mouse click, is received into theapplication output window 66″ by the network executive 50. The networkexecutive 50 forwards the raw input data to the application 62′executing on the server 34″. In this manner, the viewing user is able tointeract with the application 62′ via the HTML page 64′.

Referring now to FIG. 5, the viewing user uses a so-called “browser”program to display an HTML page 64′ having an application window 66′ onthe screen 18 of the user's computer 14. The viewing user may invokeexecution of an application program 62′. Typically this is done by theuser utilizing a “point-and-click” interface, i.e. the viewing user usesa mouse 16 to manipulate a cursor 12 that is also displayed on thescreen 18 of the viewing user's computer 14. Once the cursor 12 is overa particular portion of the HTML page 64′, the viewing user signals by“clicking” a button 15 on the mouse 16. Alternatively, the viewing usermay also signal by pressing a key on an associated keyboard 17, such asthe “return” key. In other embodiments, the viewing user may not use amouse 16 at all, but may instead use a touchpad, a trackball, apressure-sensitive tablet and pen, or some other input mechanism formanipulating the cursor 12.

In another embodiment, the application window 66′, or another portion ofthe HTML page 64′, may define a “hot zone.” When the viewing user movesthe cursor 12 into the “hot zone,” execution of the application 62′ onthe server 34″ is started.

Once the viewing user has indicated that execution of the application62′ should commence, the browser application 60 instantiates a parameterhandler 40 and passes the instantiation parameters associated with theapplications window 66′ by the generic embedded window tag 66. Theparameter handler 40 instance spawns a network executive 50 and passesto it the parameters of the application window 66′. The networkexecutive 50 determines which application 62′ is to be invoked, and onwhat server 34″ that application 62′ resides. Generally this informationis passed to it by the parameter handler 40 instance which gets it fromthe browser application 60 in the form of the generic embedded windowtag 66, but the network executive 50 may need to query a master networkinformation node 40 or other various servers, in order to determinewhich servers, if any, host the desired application 62′. The networkexecutive 50 then begins execution of the application and displays theoutput of the application program 62′ in the applications window 66′ asdescribed in detail above.

The network executive 50 continues to directly display applicationoutput in the applications output window 66″ until the viewing userindicates that execution of the application 62′ should stop, e.g. byclosing the application window 66′, or until the viewing user clicks ona tag indicating that a different HTML page should be displayed. Whenthis occurs, execution of the application 62′ can be terminated. It ispreferred, however, is to “cache” the connection. In effect, the firstparameter handler 40 instance is not immediately terminated. However,the application 62′ continues executing with a reduced priority level,i.e. in “background” mode, because the first parameter handles 40 nolonger has “focus”.

In general, it is desirable to accomplish connection caching byproviding the parameter handler 40 source code with a globallyaccessible data structure for registering instances. For example, theparameter handler 40 may be provided with a globally accessible linkedlist data structure, data array, data table, or other data structure.Because the data structure is globally available, each instance of theparameter handler 40 is able to read and write the data structure. Thisallows each instance of the parameter handler 40 to “register” withevery other instance by writing to the data structure to signal itsexistence.

For embodiments in which no other connection information is stored, apredetermined limit on the number of connections that may be cached atany one time can be set. In these embodiments if registration of aninstance would result in an excess number of cached connections, one ofthe “cached” connections is removed, i.e. the parameter handler 40instantiation associated with that connection is notified that it shouldterminate. Before termination, the parameter handler 40 notifies itsassociated network executive 50 that it should terminate. In turn, thenetwork executive 50 closes its session with the server hosting theapplication program 62′ and then terminates.

In embodiments in which other information is stored, the additionalinformation may be used to more effectively manage the cachedconnections. For example, if a user has not actively viewed an HTML page64′ in a predetermined number of minutes, e.g. ten minutes, theparameter handler 40 instantiation is instructed to terminate, thesession with the hosting server is terminated, and the parameter handler40 instance removes its entry in the registry.

Cached connection information may be managed using any known cachemanagement scheme. Connection entries may be discarded on a “first in,first out” basis, i.e. the oldest entry is discarded each time a newentry must be added. Alternatively, cached connection informationentries may be discarded on a “least recently used” basis, whichdiscards information relating to connections which have been used theleast amount by the user. Other cache management techniques, such asrandom replacement, may also be used.

If the viewing user returns to a previous HTML page 64′ having a cachedconnection, the network executive 50 associated with the HTML page 64′is returned to the foreground, i.e., it regains “focus”, and processingof the associated application resumes at a normal priority level. Ifnecessary, the network executive 50 re-establishes the connection withthe application 62′. Although no output data is stored by the networkexecutive 50 for cached connections, as soon as a connection isre-established for an applications window 66′ the connection to theapplication 62′ is re-established and the application 10 again writesdirectly to the applications window 66′.

Referring to FIG. 6, it should be noted that any client 24, 24′, 24″, orin fact, all the clients (generally 24) attached to server 34 with theapplication 63 may be another server 34′, 34″. In this manner, datatransmitted by the application 63 is sent to other servers prior tobeing sent to client nodes 24. In this manner, data transmitted by theapplication 63 is transmitted to an ever increasing number of clientnodes as this network fans out.

When each client 24 terminates its connection with the server 34, eachclient protocol stack (generally 104) and its associated minimal stack(generally 107) is destroyed. Similarly, the minimal protocol stack(generally 106) associated with the first client protocol stack 104 isalso destroyed. When the last of the minimal 107 and second (andsubsequent) client protocol stacks 104 has terminated, the configurationis as it was initially with only a first client communications protocolstack 104 associated with the execution environment 96. Note that untilall the second and subsequent client protocol stacks 104 are terminated,the first client protocol stack 104 may not be destroyed, even if thefirst client 24 is no longer present.

In such a case, the first client 24 causes the specialized application63 to execute and transmit its data to the client 24 as discussedpreviously. When a second client 24′ requests access to the broadcastapplication 63, the connection manager 80 begins to construct theprotocol stack 104′ for the second client 24′ as previously discussedwith regard to the first client 24. However, because the application 63is a broadcast application, the connection manager 80 recognizes that itneed not start an additional execution environment 96 and instead takesthe steps necessary to send the data from the broadcast application 63to the second client 24′ and any additional clients 24″.

First, the connection manager 80 creates a first minimal communicationsprotocol stack 106 which it associates with a communications protocolstack 104 of the first client 24. The connection manager 80 next createsa second minimal protocol stack 107 and associates it with thecommunications protocol stack 104′ of the second client 24′. As eachadditional client 24″ requests access to the broadcast application 63,another minimal protocol stack 106′ is created and associated with thefirst client protocol stack 104 and another minimal protocol stack 107′and client protocol stack 104″ is created for each new client 24″. Thefirst client protocol stack 104 and all the minimal protocol stacks 106,106′ associated with the first client protocol stack 104, and each pairof client protocol stacks 104′, 104″ and minimal protocol stacks 107,10′ associated with each additional client 24′, 24″ are in communicationby way of a multiplexer 121.

When multiplexer 121 is directing data to or receiving data from onlyone client 24, the multiplexer 121 is acting as a simple pass-throughdevice. However, when there is more than one client 24, 24′, 24″receiving data from or transmitting data to a single application 63,each multiplexer (generally 121) takes on two additional configurations.In one configuration, the multiplexer 121′ is configured to sendapplication data to or receive data from both the first client protocolstack 104 and each of the minimal communications protocol stacks 106,106′ associated with it. In the second configuration the multiplexer121″ is configured to send data received by the minimal protocol stack107, 107′ to the client protocol stack 104′, 104″, respectively,associated with it. In this embodiment, the mux 121 may receive inputdata directly from each client protocol stack 104, 104′, 104″.

The connection manager 80 connects the minimal protocol stacks 106, 106′associated with the first client 24 with the minimal protocol stacks107, 107′ respectively, of the second 24′ and subsequent clients 24″ andinstructs the multiplexer 121 to direct output from the application 63to the communications protocol stack 104 of the first client 24 and itsassociated minimal protocol stacks 106, 106′. The multiplexer 121 isalso instructed by the connection manager 80 to connect each second andsubsequent client minimal protocol stack 107, 107′ to its associatedclient protocol stack 104′, 104″, respectively. Data transmitted to thefirst client 24 by way of the first client protocol stack 104 istherefore also transmitted to the minimal protocol stacks 106, 106′associated with the first client 24 and hence to the second 24′ andsubsequent clients 24″ by way of their associated protocol stacks 104′,104″, respectively, and associated minimal protocol stacks 107, 107′,respectively. In one embodiment, the protocol stack container includes adata structure to keep track of the number and type of protocolsassociated with a given application 63.

Referring to FIG. 7, as discussed above, it is possible that the“clients” of one server 34 be other servers 34′ and 34″ (only two beingshown for simplicity). The second servers 34′ and 34″ then transmit thedata to clients (generally 24) or to additional servers. In thisembodiment the output of the server protocol stack (generally 104) isconnected to the protocol stacks 107′ of the secondary servers 34′, 34″.Then as described previously, the data is transmitted between theprotocol stacks and out to the clients (generally 24). In this mannerthe data may fan out and be distributed to many more clients than mayreasonably be supported by one server.

While the invention has been particularly shown and described withreference to specific preferred embodiments, it should be understood bythose skilled in the art that various changes in form and detail may bemade therein departing from the spirit and scope of the invention asdefined by the appended claims.

1. A method for displaying application output on a client node, themethod comprising: providing, by a server to a browser applicationexecuting on a client node, a data file comprising remote applicationparameters and instructions for generating, by the browser application,a first window; establishing a communication channel between a clientprocess executing on the client node and the server; executing anapplication on the server responsive to receiving a request from theclient process, via the communication channel, the request comprisingthe remote application parameters; and transmitting, via thecommunication channel, output produced by the application executing onthe server to the client process for display in a second window on theclient node, the second window generated by the client process as achild of the first window of the browser application.
 2. The method ofclaim 1, wherein executing the application further comprises executingthe application responsive to executing of a JAVA applet on the clientnode.
 3. The method of claim 1, wherein executing the applicationfurther comprises executing the application responsive to input receivedfrom an HTML page displayed by the browser application.
 4. The method ofclaim 3, wherein executing the application further comprises executingthe application responsive to selecting a tag displayed in the HTMLpage.
 5. The method of claim 1, wherein establishing a communicationchannel further comprises establishing a data pipe between the clientprocess and the application executing on the server.
 6. A system fordisplaying application output on a client node, the system comprising: aserver configured to: provide a data file to a client node, the datafile comprising remote application parameters and instructions forgenerating, by a browser application executed by the client node, afirst window; execute an application, responsive to receiving a requestfrom a client process executed by the client node, the requestcomprising the remote application parameters, and the applicationgenerating application output; and transmit the application output tothe client process for display in a second window on the client node,the second window generated by the client process as a child of thefirst window of the browser application.
 7. The system of claim 6wherein the application executes on the server responsive to outputgenerated by a page displayed within the browser application executingon the client node.
 8. The system of claim 7, wherein the client processtransmits the page output to the server.
 9. The method of claim 1,wherein transmitting output produced by the application executing on theserver to the client process for display in a second window on theclient node comprises transmitting output to the client process fordisplay in the second window, the second window generated as a child ofthe first window responsive to the client process receiving a windowhandle of the first window from the browser application.
 10. A methodfor displaying application output on a client node, the methodcomprising: receiving from a server, by a first client processcomprising a browser application executing on a client node, a data filecomprising remote application parameters and instructions for generatinga first window; generating, by the first client process, responsive tothe received instructions, a first window comprising a first windowhandle; executing, by the client node, responsive to the remoteapplication parameters, a second client process; receiving, by thesecond client process from the first client process, the remoteapplication parameters and the first window handle; and generating, bythe second client process responsive to receiving the first windowhandle, a second window as a child of the first window.
 11. The methodof claim 10, wherein generating a second window as a child of the firstwindow comprises generating the second window over the first window. 12.The method of claim 10, further comprising: scrolling, by a graphicaluser interface of the client node, the second window, responsive to auser command to scroll the first window.
 13. The method of claim 10,further comprising: transmitting, by the second client process via acommunications channel established between the second client process andthe server, the remote application parameters; receiving, by the secondclient process via the communications channel, application output of anapplication executed by the server responsive to receiving the remoteapplication parameters; and displaying, by the second client process,the received application output in the second window.
 14. The method ofclaim 13, further comprising: receiving, by the second client process,input from a user in the second window; and transmitting, by the secondclient process via the communications channel, the received input to theapplication executed by the server.